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Modeling the VLBI delay for Earth satellites / Frédéric Jaron in Journal of geodesy, vol 93 n°7 (July 2019)  

Public [article]  inJournal of geodesy > vol 93 n°7 (July 2019) . - pp 953 - 961 Titre : Modeling the VLBI delay for Earth satellites Type de document : Article/Communication Auteurs : Frédéric Jaron, Auteur ; Axel Nothnagel, Auteur Année de publication : 2019 Article en page(s) : pp 953 - 961 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] E-GRASP [Termes IGN] Geodetic Reference Antenna in Space [Termes IGN] interférométrie à très grande base [Termes IGN] point de liaison (géodésie) [Termes IGN] poursuite de satellite [Termes IGN] propagation du signal [Termes IGN] retard troposphérique [Termes IGN] système international de référence céleste Résumé : (auteur) Very-long-baseline interferometry (VLBI) observations of satellites orbiting the Earth and emitting an artificial radio signal have the potential of becoming an important technique for improving the frame ties between celestial and terrestrial reference frames. Modeling the delay of the signal reception at one station with respect to the other station of a baseline is a fundamental step for correlation and parameter estimation. The near-field VLBI delay models developed so far include numerical computation, which may become expensive in terms of computation time. This applies especially when partial derivatives are to be computed, which is the normal case for least squares adjustments. Furthermore, all the models are formulated in the barycentric celestial reference system requiring large numbers. Here we present an analytical expression for the VLBI delay for the special case of satellites orbiting the Earth, observed by ground-based radio telescopes. We analytically solve the light time equation for each signal propagation path from the source to receiver one and to receiver two under the simplification of linearizing the trajectory of the satellite. By approximating the motion of the Earth as uniform during the short signal travel times we are able to work in the geocentric celestial reference system. We investigate differences between numerical and analytical solutions by simulating VLBI observations of Earth satellites. These tests reveal that delays computed with the analytical formula are consistent with those computed with the numerical solution below the detection level of VLBI but at less computational cost. Numéro de notice : A2019-354 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1217-0 Date de publication en ligne : 20/11/2018 En ligne : https://doi.org/10.1007/s00190-018-1217-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93408 [article]

The extension of the parametrization of the radio source coordinates in geodetic VLBI and its impact on the time series analysis / Maria Karbon in Journal of geodesy, vol 91 n° 7 (July 2017)  

Public [article]  inJournal of geodesy > vol 91 n° 7 (July 2017) . - pp 755 - 765 Titre : The extension of the parametrization of the radio source coordinates in geodetic VLBI and its impact on the time series analysis Type de document : Article/Communication Auteurs : Maria Karbon, Auteur ; Robert Heinkelmann, Auteur ; Julian Mora-Diaz, Auteur ; Minghui Xu, Auteur ; Tobias Nilsson, Auteur ; Harald Schuh, Auteur Année de publication : 2017 Article en page(s) : pp 755 - 765 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] données ITGB [Termes IGN] fonction spline [Termes IGN] interférométrie à très grande base [Termes IGN] paramètres d'orientation de la Terre [Termes IGN] régression multivariée par spline adaptative [Termes IGN] repère de référence céleste [Termes IGN] série temporelle Résumé : (Auteur) The radio sources within the most recent celestial reference frame (CRF) catalog ICRF2 are represented by a single, time-invariant coordinate pair. The datum sources were chosen mainly according to certain statistical properties of their position time series. Yet, such statistics are not applicable unconditionally, and also ambiguous. However, ignoring systematics in the source positions of the datum sources inevitably leads to a degradation of the quality of the frame and, therefore, also of the derived quantities such as the Earth orientation parameters. One possible approach to overcome these deficiencies is to extend the parametrization of the source positions, similarly to what is done for the station positions. We decided to use the multivariate adaptive regression splines algorithm to parametrize the source coordinates. It allows a great deal of automation, by combining recursive partitioning and spline fitting in an optimal way. The algorithm finds the ideal knot positions for the splines and, thus, the best number of polynomial pieces to fit the data autonomously. With that we can correct the ICRF2 a priori coordinates for our analysis and eliminate the systematics in the position estimates. This allows us to introduce also special handling sources into the datum definition, leading to on average 30 % more sources in the datum. We find that not only the CPO can be improved by more than 10 % due to the improved geometry, but also the station positions, especially in the early years of VLBI, can benefit greatly. Numéro de notice : A2017-296 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0954-1 En ligne : http://doi.org/10.1007/s00190-016-0954-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85331 [article]

On the consistency of the current conventional EOP series and the celestial and terrestrial reference frames / Santiago Belda in Journal of geodesy, vol 91 n° 2 (February 2017)  

Public [article]  inJournal of geodesy > vol 91 n° 2 (February 2017) . - pp 135 - 149 Titre : On the consistency of the current conventional EOP series and the celestial and terrestrial reference frames Type de document : Article/Communication Auteurs : Santiago Belda, Auteur ; Robert Heinkelmann, Auteur ; José M. Ferrándiz,, Auteur ; Tobias Nilsson, Auteur Année de publication : 2017 Article en page(s) : pp 135 - 149 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] erreur systématique [Termes IGN] interférométrie à très grande base [Termes IGN] International Earth Rotation Service [Termes IGN] International Terrestrial Reference Frame [Termes IGN] orientation de la Terre [Termes IGN] repère de référence céleste [Termes IGN] rotation de la Terre [Termes IGN] série temporelle Résumé : (Auteur) Precise transformation between the celestial reference frames (CRF) and terrestrial reference frames (TRF) is needed for many purposes in Earth and space sciences. According to the Global Geodetic Observing System (GGOS) recommendations, the accuracy of positions and stability of reference frames should reach 1 mm and 0.1 mm year−1, and thus, the Earth Orientation Parameters (EOP) should be estimated with similar accuracy. Different realizations of TRFs, based on the combination of solutions from four different space geodetic techniques, and CRFs, based on a single technique only (VLBI, Very Long Baseline Interferometry), might cause a slow degradation of the consistency among EOP, CRFs, and TRFs (e.g., because of differences in geometry, orientation and scale) and a misalignment of the current conventional EOP series, IERS 08 C04. We empirically assess the consistency among the conventional reference frames and EOP by analyzing the record of VLBI sessions since 1990 with varied settings to reflect the impact of changing frames or other processing strategies on the EOP estimates. Our tests show that the EOP estimates are insensitive to CRF changes, but sensitive to TRF variations and unmodeled geophysical signals at the GGOS level. The differences between the conventional IERS 08 C04 and other EOP series computed with distinct TRF settings exhibit biases and even non-negligible trends in the cases where no differential rotations should appear, e.g., a drift of about 20 μas year−1in ypol when the VLBI-only frame VTRF2008 is used. Likewise, different strategies on station position modeling originate scatters larger than 150 μas in the terrestrial pole coordinates. Numéro de notice : A2017-061 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0944-3 En ligne : http://dx.doi.org/10.1007/s00190-016-0944-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84273 [article]

Co-location of geodetic observation techniques in space / Benjamin Männel (2016)  

Public Titre : Co-location of geodetic observation techniques in space Type de document : Thèse/HDR Auteurs : Benjamin Männel, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2016 Autre Editeur : Zurich : Eidgenossische Technische Hochschule ETH - Ecole Polytechnique Fédérale de Zurich EPFZ Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 97 Importance : 200 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-43-7 Note générale : bibliographie A thesis submitted to attain the degree of Doctor of Sciences of ETH Zurich (Eidg. Technische Hochschule Zürich) Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] antenne GPS [Termes IGN] Bernese [Termes IGN] centre de phase [Termes IGN] co-positionnement [Termes IGN] données GRACE [Termes IGN] géocentre [Termes IGN] interférométrie à très grande base [Termes IGN] International Terrestrial Reference System [Termes IGN] orbite basse [Termes IGN] orbitographie [Termes IGN] positionnement par GPS [Termes IGN] poursuite de satellite [Termes IGN] propagation ionosphérique [Termes IGN] repère de référence [Termes IGN] système international de référence céleste Index. décimale : 30.60 Géodésie spatiale Résumé : (auteur) This thesis describes the combination of geodetic observation techniques on-board satellites. This socalled co-location in space provides a considerable potential regarding the improvements needed to realize a long-term accurate and stable terrestrial reference frame. The space ties (i.e., the offset vectors between the on-board sensors) introduces new geometrical connections between sensors of dfferent space geodetic techniques. This space ties can be provided easily to each fundamental site via space geodetic observations. Consequently, co-location in space allows to assess technique-specific error sources as systematic effects can be addressed either to a certain station or to a certain technique. Moreover, the additional introduced orbit dynamics improve the estimation of several geodetic parameters. Within this thesis the following core topics concerning co-location in space are discussed: orbit determination, the combination of ground and space GNSS observations, and VLBI Earth-orbiting satellite tracking. Highly accurate orbit determination is the prerequisite for a suitable co-location in space. Based on the Earth observation satellite missions GRACE, GOCE, and OSTM/Jason-2 orbit determination and the impact of modeling non gravitational perturbations is studied. The overall reached orbit accuracies are at the level of a few centimeters. The combination of ground and space-geodetic GNSS observations is studied based on the GPS observations derived by 53 ground stations and the four LEOs (low Earth orbiter). Adding one LEO to the ground-only processing decreases the formal errors of weekly geocenter estimates by around 20% which is eight times more than expected due to the increased number of observations. This shows the considerable potential of the combination of ground and LEO data. Comparing the derived geocenter time series against results from satellite laser ranging (SLR) shows a good agreement for annual amplitudes, whereas the annual phases shows considerable discrepancies in the x- and the z-component. Geocenter coordinates derived from surface load density coeficients estimated in a long-term solution show a better agreement to SLR solutions but without a significant impact of additional LEOs. Using the gravitational constraint GPS satellite antenna phase center offsets were estimated based on ground and LEO observations. The results show a significant benefit for the horizontal offsets as the introduced LEOs help to dissolve limiting correlations. Concerning single-frequency VLBI satellite tracking the L4R method is introduced to derive ionosphere delay corrections based on co-located GNSS observations. A 1 cm daily station coordinate repeatability is achieved in a single-frequency GNSS processing while introducing the L4R corrections. Differences to ionospheric delays derived from VLBI observations show also a good agreement. As VLBI satellite tracking is currently in an experimental stage Monte-Carlo simulations were performed for eight different satellite orbit types. For a GNSS constellation tracking, station coordinate repeatabilities are at the level of 0.7 and 1.2 cm for a regional and a global network, respectively. Station coordinate repeatabilities of around 1 cm were derived for simulated VLBI observation to a fictitious LEO with an altitude of 2000 km. The station coordinates estimated from simulated observations to E-GRIP and E-GRASP/Eratosthenes show larger uncertainties. Based on the results suggestions for future action items regarding co-location in space were formulated. The most important recommendations are, that the combination of ground- and space GNSS observations provides a considerable benefit for the determination of several parameters and that ionosphere delay corrections should be derived from co-located GNSS observations. Note de contenu : 1- Motivation and Introduction 2- Geodetic Observation Techniques in a Nutshell 3- Reference Systems and the Combination and Co-location of Space Geodetic Techniques 4- Investigations on GPS-based Precise Orbit Determination for Low Earth Orbiters 5- Investigations on the Combined Processing of Ground- and Space-based GPS Observations 6- Investigations on VLBI Satellite Tracking 7- Conclusions and Outlook Numéro de notice : 21987 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : PhD : Sciences : ETH Zurich : 2016 DOI : 10.3929/ethz-a-010811791 En ligne : https://www.research-collection.ethz.ch/handle/20.500.11850/125751 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91982

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
21987-01	30.70	Livre	Centre de documentation	Géodésie	Disponible

Journées 2013, Systèmes de référence spatio-temporels, Paris, 16 - 18 September 2013 / Nicole Capitaine (2014)    

Public Titre : Journées 2013, Systèmes de référence spatio-temporels, Paris, 16 - 18 September 2013 : Développements scientifiques à partir de systèmes de référence de haute exactitude Titre original : Scientific developments from highly accurate space-time reference systems Type de document : Actes de congrès Auteurs : Nicole Capitaine, Éditeur scientifique Editeur : Paris, Meudon et Nançay : Observatoire de Paris Année de publication : 2014 Conférence : JSRST 2013, Journées systèmes de référence spatio-temporels, Scientific developments from highly accurate space-time reference systems 16/09/2013 18/09/2013 Paris France OA Proceedings Format : 21 x 30 cm ISBN/ISSN/EAN : 978-2-901057-69-7 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] échelle de temps [Termes IGN] International Terrestrial Reference Frame [Termes IGN] repère de référence céleste international [Termes IGN] rotation de la Terre [Termes IGN] soleil (étoile) [Termes IGN] système de référence géodésique Numéro de notice : 17019 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Actes DOI : sans En ligne : http://syrte.obspm.fr/jsr/journees2013/pdf/ Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=78597

Contient

• The ITRF and its scientific applications / Laurent Métivier (2014) 

Documents numériques

en open access Journées 2013, Systèmes de référence spatio-temporels Adobe Acrobat PDF

Introduction à l’astronomie de position / Jonathan Chenal (2012)

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Towards a combination of space-geodetic measurements / Arnaud Pollet (2012)  

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Le repère céleste de références : définition et amélioration / Anonyme in Géomatique expert, n° 81 (01/07/2011)

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Introduction à l’astronomie de position / Jonathan Chenal (2011)

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On the accuracy assessment of celestial reference frame realizations / Z. Malkin in Journal of geodesy, vol 82 n° 6 (June 2008)  

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Vers un futur repère de référence céleste : Journées 2007, systèmes de référence spatio-temporels, Paris, 17-19 septembre 2007 / Nicole Capitaine (2008)  

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Journées 2005, systèmes de référence spatio-temporels, Warsaw, 19-21 September 2005 / Alexander Brzezinski (2006)  

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Proceedings of the IERS Workshop on Combination Research and Global Geophysical Fluids, Bavarian Academy of Sciences, Munich, Germany, 18 - 21 November 2002 / Bernd Richter (2003) 

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Stabilité du repère de référence extragalactique / Karine Le Bail (2000)

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Analyse de repères célestes VLBI au moyen des harmoniques vectorielles / X. Oviedo (1996)

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